messages view problem

some accounts of our organization have problem to display emails in their mailbox. Foe example, in left panel we can see in inbox directory 6 mails but in the main panel show up only one. Where are other mails? We have no filters and share folders set. We use web client only. Any help will be appreciate

Currently we are using mozzilla, but same is with IE7. After cleaning cache and restarting zimbra (zmcontrol stop|start) I find now just 1 message (instead of 6). Now I try to restore all files. Thank you for your help